Continuous casting machines with two counter-rotating casting rolls in between which molten metal is cast are known. (Herrmann, Handbook on Continuous Casting, edition 1980, p. 63, 64).
The casting rolls, hereafter called rolls generally consist of a roll core with a neck on both ends to accommodate the bearings, of a roll shell which is firmly fitted to the core and of the requisite components such as rotating glands, tubes, distribution pieces, gaskets and various small parts for the transportation of the coolant to and from the machine.
The roll core has grooves on its surface through which the coolant flows, whereby the heat which is conveyed from the cast to the shell is removed.
It is known to arrange the grooves in a circumferential direction or in a helical manner around the circumference or parallel to the axis of the roll core.
The outside surface of the shell which is exposed to thermal strains must be periodically reworked and the shell which is to be considered as a wearing part must finally be replaced.
Independent of the shape and arrangement of the grooves the shell is subject to a creeping motion on the surface of the core due to local, external heating and internal cooling, thus causing uneven wear of the core which therefore has to be remachined on a lathe by turning or grinding of the surface whereby the diameter diminishes accordingly.
In order to maintain the cross-section of the grooves for the flowing through of the coolant they must be reworked from time to time, a circumstance that demands a high expenditure of labour and corresponding work facilities. Finally, when the minimum diameter is reached the expensive roll core must be replaced.
Placing the grooves parallel to the axis of the core has a great advantage over other arrangements due to the fact that they can easily be cleaned by a rod with a corresponding cross-section, which can be pushed through the grooves in order to remove any sediments such as rust for example without removing the shell.
On the other hand the reworking of grooves that are parallel to the axis of the core is more laborious than that of grooves which are arranged in the circumferential direction of the core, due to the fact that the latter can be cut on a lathe in the same operation as the core surface is redone whereas the former have to be reworked on a milling or planing machine.
The remachining of the roll cores is costly. Furthermore the new shells have to be adjusted to the diameter of the corresponding roll core in order to ensure the requisite fit. This circumstance demands an individual production or the stock-keeping of shells with various inside diameters.